Burglar alarm system



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Patented Apr. 21, 1953 UNITED STATES PATENT BURGLAR ALARM SYSTEM Earle V. Gardiner, Chicago Heights, Ill.

Application April 19, 1951, Serial No. 221,919

(Cl. :M-213) 9 Claims. 1

This invention relates to a control device for alarm systems and has for its principal object the provision of a new and improved device of this type.

Itis a main object oi the invention to provide a control device for an alarm system, such as a burglar alarm system, that operates on commercial current, which control device turns on the system at a prescribed hour, turns on the system at a prescribed hour, prevents sounding a false alarm in the event that the voltage of the commercial current falls below a safe operating minimum o1` is interrupted, and restores the system to operative condition upon the return to normal ci the current supply.

Another object of the invention isto provide a control device for an alarm system which permits testing the system preliminarily to placing it in service to make sure that it is in condition ior proper functioning.

Another object of the invention is to provide a control device for alarm systems, which can be added to existing system of this type.

Further objects of the invention not speciilcally mentioned here will be apparent from the detailed description and claims which follow, reference being had to the accompanying drawing in which the invention is shown by usual schematic circuit symbols.

Alarm systems such as are commonly employed as burglar alarms are of two general types: first, a light ray system, and, second, a foil tape system. Such systems are placed in operation when premises are left unattended and arranged to give an alarm signal should the premises be entered while the system is in operation, which signals are either audible and visual at the premises, or audible and visual at a central watch station, such as a police station, or both.

In the case of a light ray system, power is usually taken ofi of commercial lines, most generally llO volts alternating current. This power is utiliaed to activate a source of light, usually invisible light such as infra red., which is reflected about the premises and picked up by a photoelectric cell to control the current output of an amplifier unit that maintains a relay operated as long as the light beam is continuous. Interruption of the beam causes the relay t0 drop back thereby operating an alarm signal to indicate trouble at the premises.

Such systems are sensitive and in the event that the voltage of the source of current drops below a definite minimum value or is interrupted even momentarily, .false alarms result. Once the systemhasl been tripped andthe alarm signal operated, the operation continues until the premises is visited and the alarm turned oi.

The present invention. provides a control device which contains marginal relays maintained operated when the system is in operation and arranged to restore at a voltage value slightly higher than the minimun upon which the system operates successfully. Thus, in the event that the voltage of the source of supply drops, the marginal relays restore and through circuits controlled thereby disable the signal t0 prevent a false alarm. As soon as the voltage returns to normal, reset mechanism in the control device re-operates the relays to ire-condition the signal for normal operation. ln the event that the source of supply fails completely, even for a m0- ment, the signal is likewise disabled and restored to operative condition as soon as the voltage of the source of supply is restored.

It is common practice in burglar alarm systems to provide a clock that is arranged to turn on the system at a prescribed hour and to turn it on again at a prescribed hour. The control device of the present invention includes such a clock switch and incorporates also a testing arrangement so that when the proprietor of the premises is preparing to close for the day he can test the alarm system to make sure that everything is in readiness for normal operation when the clock switch operates.

In the case of the foil tape type systems, a conducting tape is att ched to windows and the like and connected in series with door-operated switches which are included in a circuit with local batteries to maintain energized an alarm control relay while the system is in operation. Breaking of this series circuit trips the alarm which is then operated usually from commercial current. The control device of the present invention is also adaptable to systems ci this type, although the need for such a control in such systems is not as great as in the case of systems operating completely on commercial current.

Referring now to the drawing, the apparatus included in the lined-off area i may be an existing burglar alarm system comprising a source of light 2 which directs a beam 3 onto a photoelectric cell 4 that controls an amplier 5, the output tube S of which has a relay "i connected in its plate circuit. The relay 'i carries a mainspring B which is closed against its make contact when the beam 3 is continuous and after the ampliner unit has warmed up. Interruption of the beam 3 causes the relay l to restore, thereby opening spring 8 from its make contact to sound an alarm.

The maximum length of light beam 3 that can .aeeaiee be used is ortentimes insui'cient to 4cover a premises, in Which `case several units are employed with the alarm circuit extended through these units in series. Such additional units are indicated at Ic vand Ib, and since these units duplicate unit I, only the alarm circuit springs 8a and 8b are shown.

The control device of the present ,invention `is lconnected to a Vsource of commercial current, usually alternating current, designated vlby terminals L-I and L-2, through a suitable fuse I4, and consists of a clock II preferably an electric 'clock whose motor is connected across the line over the obvious circuit. The control device also consists of a source of direct current vI 2,*compr`ising a transformer I3 1and a full lwave rectier `I4 which may be a selenium cell rectiiier, the output terminals of which are bridged by a condenser I5 and resistance I'S to smooth out undulations in the output current of the rectier.

The control equipment also contains a testkey I'I by Which the loperative ,conditionvof the system is determined irrespective of the position of the clock switch.

The details of the 'control device Will best be understood by a description of a typical operation. Upon vpreparing to lea-ve the premises, test key .Il isoperated'to move spring I8 into engagement Ywith its make contact and to move spring I9 away from its break contact. A lcircuit may now be .tracedfrom the :L-Z terminal over conductor 2,0, conductor 2l, through spring I3 and its make contact, 'conductor Z2 to the alarm systems I, -Ia and Ib, thereby yconnecting the .light sources and amplifier units across the line to conductor 23 which leads to the vL--I terminal ofthe commercial current. The ylight sources and amplifiers are thus put into operation and after a brief Warm-up period relays l energize, Vprovided nothing obstructs kthe path of the light beams. lIn many instances Where such a beam is extended Vacross' stock bins containing valuable equipment, misplacement of such equipment will interrupt ,the beam and consequently relay l will not operate. Such a `condition will 'be readily apparent and steps can be taken to correct it.

Light beams limobstructed Assuming that none of the light beams v3 is cbstructecLithe :relay .l iineach of vthe units i, Ia

land I'b will Voperate and Vclose ltheir respective springs .i8 against their make contacts. A cir- .cuit may now be traced vfrom L-l, through fuse Ill, .conductor 23, spring 8 and its make contact,

spring 8a and its make contact, spring 8b and i,

In the event that one of the light beams 3 is obstructed, one of the relays l will not energize and 'the foregoing circuit or relay 25 will'not be closed and that 'relay will not operate. Included on the control panel is .a push button svfitch for each of the alarm units vdesignated as BT, BaT and SbT. The operator, noting Ythat relay 25 has not operated, pushes 8T, thereby shunting springs .8 of'unit I. If the beam 3' vof unit I is unobstructed and itis spring 8 that is holding the circuit of relay 25 open, the above circuit of relay V2t will be completedthrough 8T and relay 2.5'wil1 be operated. Through keys 8T.

conductor 22.

SLLT and SbT, the obstructed light beam can be located and steps taken to clear the obstruction.

Control unit operation Relay 25 upon operating moves mainspring 28 away from its break vcontact into engagement with its make contact, thereby completing a circuit from the Vnegative `terminal ,of the rectifier unit ,I4, conductor 29, .spring ,2B and its make contact, through condenser 3Q, through the Winding of direct current trigger relay SI and thence back to the positive terminal of the rectifier over During the interval that condenser .33 is accepting a charge, sufficient current Will flow through the winding of relay 3I to operate 'that relay which moves spring 33 into engagement with its make contact, thereby closing a circuit from the L-2 terminal of the commercial current on conducto-r 2, conductor 34, through resistance 35, through the winding of alternating current relay 36 to the other side oi" the commercial line. Relay -36 operates over this lcircuit and closes spring 37 4against its make contact, thereby establishing 4a holding circuit for the relay extending to the conductor 2l independently of the spring 33'.

A circuit may now be traced from conductor 2l through spring 37 and its make contact, lconductor 34, conductor 38, through the Winding of lalteinatingrelay current 39 to the L-'I terminal of commercial current over conductor 44. Relay 3'2 operates over this circuit.

A circuit may noW be traced from negative on conductor 29 through spring 4II of relay :39 and T its make contact, through condenser l42, Ythrough the Winding of direct V-current trigger relay 43 to positive on conductor 32. During the interval that condenser 42 is accepting a charge, relay 43 operates, thereby closing springl44 against its make contact, to extend the circuit from conductor 2:7 through the Winding of relay V45 to .the L-l terminal vof the .-source `of power, over conductor 45, conductor 24, springs 8, Scand 3b and their `respective make contacts, and the conductor 23. Relay 45 operates over this circuit, moving mainspring 4.7 into .engagement with its make contact thereby locking itself to conductor 21 independently of springs 44.

When commercial current 4is placed von conductor 24, as explained above, visual signal 551s connectedacross the `source of current in series .with aresistance 55. .Signal may :conveniently be a neon glow tube which is thus lighted to indicate .that the alarm system is in proper Working order. Y

The foregoing ytest may be extended to include a test of the control equipment and alarm system. To do this, the test key :is maintained in operated position vand a light beam .3 is intentionally broken. Relay 'I Will drop back and open springs S, Vremoving the L-I potential from conductor 45. Relays 45 and 25 drop back. A circuit may now ce traced 'from'L-'Z 'potential on conductor Y2l, 4spring 41 and its break contact,

- spring 152 and its make contact, conductor ;5I,

I maintained operated during the test, relay 45 remains unoperated and signal S0 .continues 4.to

break contact now open because relay 45 is operated, to commercial current on conductor 21, the other side of the signal device being connected to the L-l terminal of commercial ourrent over conductor 53.

Test key l1, which is preferably a non-locking key, is biased to return to operate position, in which it is shown in the drawing, as soon as released, thereby insuring that the system will not inadvertently be left in non-operating condition.

The test having thus been completed, the proprietor closes the premises and leaves, and `nothing happens until the time at which clock Il is set to turn on the system.

When that hour is reached, the clock closes mainspring 51 against its make Contact, thereby .l

extending conductor 26 to conductor 22 and conductor 21. Power is thus supplied to the alarm system l as before, and as soon as that system has warmed up and the relays 1 operated, relays 25, 3|, 36, 39, 43 and 45 operate in the above described manner. Glow light 55 operates to indicate that the system is in operation.

Low voltage operation The control device guards against false alarms due to failure of the apparatus because of low voltage through the use of maginal relays that are bridged across the line when the apparatus is in operation. Alternating current relays can be made marginal in a number of ways, such as by the use of saturable reactors or by shunting the relay with resistors. In the example shown, the winding of relay is shunted by a resistance 58 and the winding of relay 36 is likewise shunted by a resistance 59, these resistances being of high ohmic value, in one instance '1500 ohms each. Resistances 26 and 35 being connected in series with the parallel circuits through the windings of the relays and resistances serve to make relays 25 and 36 marginal and incapable f of remaining in operating position when the voltage supply to them falls below a definite value, for example 105 volts.

In the event tha the voltage of the source of alterntaing current falls below this minimum, relays 25 and 36 will restore to normal. Relay 36 thus opens spring 31 from its make contact, breaking the previously traced circuit for relay 39, causing that relay to restore, and at spring 52 to open a point in the circuit of signal l5D to prevent an operation of that signal. Relay 25, upon restoring, moves spring 28 into engagement with its break contact, thereby short-circuiting condenser 36 to discharge that condenser. Relay 39, upon restoring, moves spring 4l into engagement with its break contact, thereby short-circuiting condenser 42 in a similar manner.

The reduction of voltage to the value taken by way of example may cause the current supplied to relays 1 by the amplifiers 5 through output tubes 6 to fall sufficiently to cause these relays to restore and thereby open the previously traced circuit for relay 45 which restores and closes spring 41 against its break contact, thereby closing a point in the circuit of alarm signal 6 however, nothing happens, since the circuit for that signal is now opened at spring 52.

Voltage restores to normal As is usually the case, fluctuations in voltage of a commercial source of supply are but momentary, and after a short interval the voltage returns to normal. The alarm system not having been tripped, relays 1 will again operate, whereupon relays 25, 3l, 36, 39, 43 and 45 will be re-operated as before. Thus it will be seen that a momentary dropping of the voltage of the source of supply is prevented from turning in an alarm which would be false.

Voltage failure Occasionally commercial sources of power fail completely. Relays 36, 25, 39 and 45 being operated by such current will automatically restore. Restoration of relay 39 opens a point in the signal circuit as before and no false alarm is given. Upon restoration of the commercial current, which usually takes place after a brief interval, the alarm system warms up again and the relays 1 re-operate, whereupon the control device repeats the above described cycle of operations to re-condition the system for operation.

The alarm system is tripped Assume now that an intruder enters the premises and thereby breaks the beam of light 3, even momentarily. Immediately the beam is broken, relay l restores and the circuit over which relay c5 is maintained operated is thus broken and that relay restores. A circuit may now be traced from the commercial current on conductor 2, spring 51 and its break contact, spring and its make Contact, conductor 5E, test key spring $9 and its break contact, through the signal 56 to the other side of the source of power on conductor 53. The signal operates to sound an alarm. Even though the beam .be immediately restored and the L-l circuit immediately reconnected to conductor 24, relay 45 cannot reoperate so long as relay 39 remains operated, and the signal 5t will continue to operate until the system is turned off at the premises.

shutting op* the system When the clock H opens spring 5l from its make contact, as it will when the turn off hour is reached, the L- connection is removed from conductors 22 and 2l, and all relays in the system restore. The transformer is removed from across the line and the system is completely disconnected froni the line save for the motor of clock il.

From the foregoing it will be apparent that the control device of my invention guards an alarm system from false alarms occasioned by a loss of voltage of the commercial source of current supply, even though that drop in voltage is not complete. rihe control device also functions when the source of commercial current is interrupted. En either event, as soon as conditions are restored to normal, the alarm system is restored to normal so that tripping of the system will soun-:l an alarm in the usual manner.

While I have chosen to show my invention by illustrating and describing a preferred einbodiment of it, l have done so by way of example only, as there are many modications of the specific details shown and adaptations which can be made by one skilled in the art within the teachings of the invention.

' Having.A thus coin-plied with the. statutes; and.

shown andiY described a preferred: embodiment. of my invention, what I consider new and desire to have patented; byLetters-Patent ispointed out in the., appended claims.

Whatis claimed is:

l... Tne-l combinaticnwith. plurality of. alarm units containing a relay-v that. iS. nolmail energized when thev system is in-,operationand is de energized to.. initiate an operation ci signal when thesystem; is tripped; of a control; deyice comprising. aV relay operated over: a circuit: ex.:= tended; through Contacts. on said unit. relays; series; a second relay operated; under;tlle..contro1 of said iirst relay to close a point in the circuit of the signal; means including marginal relays forv restoring: said, second. relay when, thev voltage onL the.. system falls .below amil lmum. .State operating value. thereby to prevent restoration of. a unit. relay because 01",. said low voltage.from o ating said sigl al;` and means.inclllidingv a t Nr relay for reoperating.1 said-:second relay when1 nora mal voltage. is restored.

Ina control. unit, a source of. direct current, a. directeur-rent .1 ay, a condenser, an. alternating current relay, contacts; onsaid. alternating cur-V rent relay closed byv the relay in. operated posif tion for closing a circuit from said source through said condenser and; direct. current relay in series to. operate the relay momentarily While said con- I denser is acceptingva charge; a second alternating current relay; contacts on said direct current relay closed by the. relay in operated position for closing a circuit for said second alternating current relay to operate that relay;` and contacts on said second alternating current relay for closing a holding circuit for the relay.

ln an alarm system in which an alarin circuit is opened when, the system is tripped to effect the operation of a signal device; a control relay; contacts on said relay closed when the relay is operated to close a. pontin the circuit of said signal device; means including a marginal relay for operating and maintaining, Saidcontrol relay in. operated position, said marginal relay restoring said control relay when the voltage on said system drops to preventoperating the signal device when said alarm circuit is opened by said drop in voltage.

e. In a control unit for an alarm system that operates on commercial alternating current, a

voltage marginal alternatingv current relay, a trigger relay,l means for momentarily operating said trigger relay, a circuit for said marginal relay closed by said trigger relay in operated position to operate the marginal relay, a holding circuit for said marginal relay closed through normally open contacts on that relay to hold the relay in operated position irrespectiyevr of the position ci the trigger. relay,y a circuit for the alarm` of said system,A and contacts in said circuit operated under the control of said marginal relay and opened when thev marginal relay restores to disable the alarm when the voltage supplied to the system falls too low.

5` A control unit as claimed in claim 4 ln which. the means for momentarily operating, the. trigger relay comprises a second marginal alternating current relay whose circuit remains closed across the line so that the relay re-energizes when. the voltage is restored to.v normal thereby to reoperate the trigger relay to re-close the circuit of the first marginal relay.

5. A control unit as claimed in claim. in which the means for momentarily operating. the

trigger-relais comprises e. Second marginal alternating current relay, a. circuit iorsairlV second rela-y controlled by. the alarmi systemnand closed when. the system; 1s;in operating.. condition to op-V crate. thesecondz marginali. relay when the volt.- age-.returns toinormal therebyY to refoperatethe. trigger: relay to. re-close thecircult ofthe. rst marginali relay;

7 The combination.with-an; alarmsytenr having a; signal; and, a. relay igor controlling. thatsige nal, wlriclr relay is inV operated position when the system is in. operation. and restores when the` system is. tripped-, thereby to operate. the signal; or a control unit forthesystem compris.- inga signalA relay, circuit means over which; said signal" relay is. energized when the system relay is. in.- operated position, a marginal relay connected acrossthe. source oi commerciali current when` the.- systern. isi-n operation and, maintained in operated pcsiticnsoiong as thevoltage of said source. exceeds. the. minimum requiredV bythe sys,- tem, acontrolY relay, a circuit fon saidV control relay closed through normallyY open contacts on said.x marginali relay overwhich said control relay operates.. when the marginal relay is operated, and. a. circuit for said signalV extending through normally. closed contactson said signal relay and normally open contacts on said control rela-y; which circuit is opened when the control relay restoresto preventV operation off the signal when the voltage-.ialls below said. minimum irrespective of the posi-tion: oi the system.` relay.

8. A control uni-t for an alarm system, in which a relay restores Whenthe systemv is tripped to operate a.. signal, for disablingY said.. Signal when they current .supply to, the` system is. interrupted, and for. restoring. the signal. to. oneratye condi.- tion when said. Supply is restored comprising: a Source of. direct current; a direct current relay.; acondenser; analternatins currentrelay; acircuitforsaid alternating currentrelay closed by contacts on. the System-.relay that, are closed when that relay isoperated, tooperate the alternating current relay.; a circuit for. Said direct current relayclcsed by contacts on said. alternating current relay to connect said condenser and relay in Series. across-said source. of direct. current.. to. operate. Saldreloy momentarily as` the, condenser is; accepting. a charco; a. second alternating oui'.- rent, relay; a circuit. for Saidsecond relay closed bycontacts. onsaid. direct. current 1161215. in. 0.1%'

erated nosition to .connect theseoond relay across. said current supply to operate the secondV relay; a holdingE circuit. for Said second relay; a control relay tloroueh normally open. Conta-cts ony which the signal Circuit extends.; a circuit for Said con.-4 trol relay. closed by said secondrelay inoperated nositonrsaidrst and second alternating Current relays restoring.y when Said Current sup-ply is. lnterrupted thereby. to. restore .said control relay and openthesie .cir-cuit; and. contacts said. A n ing current relay closed when the re restores. iol-Snort-.Cirouitine said condenser thereby prepa-tine Seid direct current relay for .eration when said Iirst alternating current rfc-onoratesresnonsiye to restoration ot Said our-v rent supply..

9.. lire c lamination with. an alarmsystem.. having;a.,slen a d relayY for controlling; that Sie nal which. re. y is operated position when the system is. pee-ration andrestoreswhen the. sys.- telnistripped. t. ereby to oper... e the Sie-nal; of.; control; unit. lon the system, comprisiner; a source ci commerical alternating current.: a clock seiten-connected. across said` source, of: current.

assunse 9 and operated thereby to connect the system to said source at a prescribed time and to disconnect the system therefrom at a prescribed time; a marginal alternating current relay; a circuit for said relay closed through normally open contacts on the system relay, When that relays moves to operated position to place the system in operation, to connect the marginal relay across said source of current; a source of direct current in said unit; a direct current relay; a circuit for connecting said direct current relay to said source of direct current closed by said marginal relay in operated position to operate that relay; a second marginal alternating current relay; a circuit for connecting said second marginal relay across said source of alternating current, closed by said direct current relay in operated position to operate the marginal relay; ya holding circuit for said second marginal relay closed by that relay in operated position; a circuit for said signal; a control relay operated over a circuit closed by said second marginal relay in operated position to prepare a point in said signal circuit; a second direct current relay; a circuit for said second direct current relay closed by said control relay in operated position to connect said second direct current relay across said source of direct current thereby to operate -that relay; a signal relay; a circuit for said signal relay closed by said second direct current relay in operated position and extending through contacts on said system relay, to operate the signal relay; and normally closed contacts on said signal relay included in said signal circuit to close that circuit to operate the signal when the system is tripped and the signal relay thereby restored, said second marginal relay restoring when the voltage oi' said alternating current source falls below a definite minimum thereby restoring said control relay and opening said signal current yto prevent an operation of the signal should the system relay and signal relay restore because of said low voltage.

EARLE V. GARDINER.

References cited in the me of this patent UNrrED STATES PATENTS Number Name Date 1,672,049 Almquist June 5, 1928 1,789,566 Spray Jan. 20, 1931 1,909,212 Muehter May 16, 1933 2,249,891 Ekman et al July 22, 1941 2,294,043 Nicon Aug. 25, 1942 2,439,405 Zierdt, Jr Apr. 13, 1948 2,469,001 Poitras May 3, 1949 

